While not limited thereto, the present invention is particularly adapted for use with power-pipe tongs used in oil well drilling operations. Such power tongs are provided with a torque indicator device used to determine the amount of torque the tong applies to a drill pipe in making up a drill string. In the usual case, the torque indicator device is attached at one end to a radially-extending arm on the tong and at the other end to a fixed point such as the oil well drilling derrick. The arrangement is such that when torque is applied to a drill string by an internal motor built within the tong, the entire assembly will tend to rotate about the pipe and is retrained from doing so only by the connection of the torque indicator device between the radially-extending arm and the derrick or other fixed point of connection.
Torque indicators of this type basically comprise a hydraulic cylinder arranged to pressurize liquid in response to a torque-producing force, and a pressure gage connected to the cylinder which is calibrated in foot-pounds. A difficulty with prior art torque indicator devices of this type is that they are calibrated for a single torque arm length, meaning that a different torque indicator device is needed for each torquing tool of a specified moment arm.